Wood drill

Abstract

A wood drill includes a clamping portion for connecting, for conjoint rotation, to a tool fitting of a portable power tool, and a head portion which is provided with a centering geometry. The clamping portion is formed at a first end, remote from a workpiece, and the head portion is formed at a second end, close to a workpiece, of the wood drill. The clamping portion is connected to the head portion via a shank portion. A maximum outside radius of the head portion is greater than a maximum outside radius of the shank portion. The head portion has at least one main lip with at least two stages for introducing a bore with a predefined inside radius into a workpiece. An outside radius of a main lip base is less than 60%, preferably less than 50%, of an outside radius of the head portion.

The invention claimed is: 
     
       1. A wood drill bit, comprising:
 a clamping portion configured to be connected in a rotationally fixed manner to a tool receiver of a hand-held power tool; and 
 a head portion provided with a centering geometry, 
 wherein the clamping portion is located at a first end of the wood drill bit that faces away from a workpiece and the head portion is located at a second end that faces toward the workpiece, 
 wherein the clamping portion is connected to the head portion via a shank portion, 
 wherein a maximum outer radius of the head portion is greater than a maximum outer radius of the shank portion, 
 wherein the head portion has at least one lip that comprises at least two steps for drilling a hole of a predefined inner radius into the workpiece, 
 wherein an outer radius of a lip base of the at least one lip is less than 60% of an outer radius of the head portion, 
 wherein a profile angle of between 10° and 30° is defined between the at least one lip and a perpendicular plane to a longitudinal central axis of the drill bit, 
 wherein the at least two steps of the at least one lip are axially spaced apart from one another by one step height that is defined as a distance between adjacent steps of the at least two steps, 
 wherein each of the at least two steps of the lip has a radial step width, and 
 wherein the radial step width is greater than the step height, 
 wherein the head portion has a helically coiled surface geometry, and 
 wherein the helically coiled surface geometry defines at least one chip groove and at least one minor cutting edge. 
 
     
     
       2. The wood drill bit as claimed in  claim 1 , wherein the radial step width is between 1 mm and 10 mm. 
     
     
       3. The wood drill bit as claimed in  claim 1 , wherein each step base of the at least two steps is inclined in each instance by a step angle defined perpendicularly to the longitudinal central axis in the direction of the first end of the wood drill bit. 
     
     
       4. The wood drill bit as claimed in  claim 3 , wherein the step angle is between 0° and 65°. 
     
     
       5. The wood drill bit as claimed in  claim 1 , wherein:
 a wedge angle is defined between the at least one lip and an edge of the at least one chip groove, and 
 the wedge angle is approximately 60°. 
 
     
     
       6. The wood drill bit as claimed in  claim 5 , wherein:
 a rake angle is defined between the edge of the at least one chip groove and the longitudinal central axis. 
 
     
     
       7. The wood drill bit as claimed in  claim 1 , wherein the centering geometry is configured in the manner of a screw having a helically encircling thread that has a pitch. 
     
     
       8. The wood drill bit as claimed in  claim 7 , wherein the pitch of the thread is between 1 mm and 2.5 mm. 
     
     
       9. The wood drill bit as claimed in  claim 1 , wherein the wood drill bit is made with a high-strength carbon steel. 
     
     
       10. The wood drill bit as claimed in  claim 1 , wherein the outer radius of the lip base is less than 50% of the outer radius of the head portion. 
     
     
       11. The wood drill bit as claimed in  claim 1 , wherein the radial step width is between 2 mm and 5 mm. 
     
     
       12. The wood drill bit as claimed in  claim 3 , wherein the step angle is about 40°. 
     
     
       13. The wood drill bit as claimed in  claim 1 , wherein the profile angle is between 15° and 25°. 
     
     
       14. The wood drill bit as claimed in  claim 1 , wherein at least the at least one lip or cutting edges of the at least one lip are formed with a high-speed steel and/or with tungsten carbide.